This invention relates to simulated perspective displays and more particularly relates to such displays employing digitally coded and stored information concerning faces of objects comprising an area to be viewed.
Digital image generators (DIGs) are computer based systems which utilize a large base of data representing coordinate information for points representing the vertices of polygons. These polygons are grouped to form objects which, in turn, are arranged to form an area in the world to be viewed.
For an understanding of the operation DIG's it is recommended that the following U.S. Pat. Nos. be studied: 4,077,062 entitled "Real-Time Simulation Of A Point System With A CRT Blank Period To Settle Beam Transients", which issued in Feb. 28, 1978 to R. G. Nielsen; 4,152,766 entitled "Variable Resolution For Real-Time Simulation Of A Polygon Face Object System", which issued May 1, 1979 to R. C. Osofsky et al.; 4,179,823 entitled "Real-time Simulation Of A Polygon Face Object System As Viewed By A Moving Observer", which issued Dec. 25, 1979 to J. B. Sullivan et al.; 4,179,824 entitled "Simulation Of An Object System Formed By Polygon Faces Having A Series Of Fundamental Shapes and Dimensions", which issued Dec. 25, 1979 to D. R. Marsh; 4,181,953 entitled "Face Vertex Correction For Real-time Simulation Of A Polygon Face Object System", which issued Jan. 1, 1980 to R. C. Osofsky; and 4,208,719 entitled "Edge Smoothing For Real-time Simulation Of A Polygon Face Object System As Viewed By A Moving Observer", which issued June 17, 1980, to R. W. Lotz, et al.
The aforementioned patents disclose DIG devices which access in real time the aforementioned vertex data and by means of a series of stages of translation, rotation, clipping and projection, which stages together comprise an "image processor", organize the vertex data accessed according to a current display scene. This scene is reconstructed many times per second to allow for a continuous series of such scenes to present a moving picture. The current display scene data is utilized to generate a video signal which drives a CRT viewed by, for example, a flight simulator operator, who is thus presented with a realistic dynamic scene based on the accessed data.
In a typical "flight" scene presented by such a DIG the number of visible faces in each current display scene varies as the simulated flight proceeds. During a complex or close range scene, the high number of visible faces may temporarily exceed the data handling capability of the image processor. This overload condition may be minimized by eliminating non-critical faces such as those faces currently having a display size below the visibility threshold or smaller than one scanline in height. It is believed that prior to this invention no means were available which functioned to eliminate such non-critical faces.